Art of making pulp for paper



Patented May Ed, ldzd.

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BERTBAND S. SUMMERS, 01? PORT HURON, MIGHIL'GAN.

ART OF MAKING PULP FOR EALM.

Ito Drawing.

cium or magnesium or both. The liquor is commonly believed to contain a bi-sulfite or a sulfite of the base dissolved in free sulfurous acid with an excess of the acid present. Digestion with bi-sulfite liquor tends to weaken the fiber, particularly where flax or other straws are treated, and even in the digestion of wood fiber some of the cellulose is lost by the energetic action of the liquor. In the alkali process, which is more particularly used in the digestion of resinous woods which are not suitable to the sulfite process, the digestin liquor commonly contains 15 to of tie alkali on the weight of the fiber treated in alkali. Ordinarily the pulp resulting from the alkali treatment is a soft open pulp used primarily for book paper. 25 Where greater strength is desired in the product of the alkali process a mixture primarily of caustic soda and sulphide of soda, formed from salt cake or sulfate of soda'is employed, this form of the alkali process being known as the sulfate process. It produces a very strong pulp, but the latter has the disadvantage of being difficult to bleach and losing much of its strength during the bleaching operation.

I have found that when a suitable proportion of a soluble phosphate is added to the liquor whether acid or alkali better results are obtained, in the case of the sulfite liquor the weakening or devastating effect of the liquor on the fiber being greatly decreased and the yield of pulp increased, and in the case of the alkali process the resulting pulp is much stronger and may be bleached to give a rugged product, equaling in strength the strongest sulfite pulp.

Except for the addition of the phosphate the digesting process of my invention, whether soda or alkali may be carried out in substantially the well known manner. The phosphate is merely added to the liquor before or when the latter is charged into the digesters and the procedure is carried out according to the usual practice. The amount of phosphoric acid added may vary within wide limits, depending upon the material be- Application filed December as, 1923. Serial in. 682,310.

ing treated and the nature of the product desired, but I prefer to use between 1 and 4% of the weight of the fiber treated or a soluble phosphate (dry weight) such as sodium phosphate. I have successfully used, W however, as much as 10% phosphoric acid though ordinarily satisfactory results may be obtained within the narrower limits given, a stronger pulp resulting from the use of the higher percentage. In case trisodic M phosphate, which I prefer for the purpose,

is used in the alkali process the phosphoric acid remains combined with the base. In the use of the salt in the acid process a certain amount of free phosphoric acid results. 79 As the different mono-hydrogen, (ii-hydrogen and tri-hydrogen phosphates readily change one to another according to the acidity or basicity of the solution it is simply necessary to compute accordingly the amount of phosphoric acid required for the kind of pulp desired from the particular process employed. In the case of the more readily weakened fiber such as flax in which it is necessary to pulp the wood celluloses and the pectocelluloses at $9 the same time I have found it desirable to use somewhat larger amounts of phosphoric acid, it being possible to use materially more than 4% without injury to the product although in the alkali process the pulp tends 95 to'reach a harder state with less amounts of phosphoric acid than is the case with the acid process.

ll claim:

1. A process of making pulp from vegetable fiber which consists in digesting same in a liquor containing a digesting agent and phosphoric acid.

2. A process of making pulp from vegetable fiber which consists in digesting the same in a liquor containing a digesting agent and a soluble phosphate.

3. A process for making pulp from vegetable fiber which consists in digesting the fiber in a liquor containing a digesting agent 1 and a sodium phosphate.

4. A process of making pulp from vegetable fiber which consists in digesting the fiber in a solution containing any alkali and a phosphate soluble in the'presence of the W5 alkali. i

5. A process of making pulp from ve etable fiber which consists in digesting t e fiber in a liquor containing caustic alkali and a soluble phosphate. are

6. A process for making pulp from vegetable fiber which consists in digesting the fiber in a liquor containin a digesting agent and from 1 to 4% of pfilosphorie acid in soluble form.

7. A process of making paper pulp which consists in digesting fiber in a solution containing caustic alkali and 1 to 4% of sodium phosphate.

8. As a composition of matter a liquorfor digesting vegetable fiber for producing paper pulp comprising a digesting agent and phosphoric acid.

9. As a composition of matter, a liquor for digesting vegetable fiber to form paper pulp comprising a digesting agent and a soluble phosphate.

10. As a composition of matter a liquor for digesting vegetable fiber to form paper pulp comprising an alkali and a phosphate soluble in the presence of the alkali.

BERTRAND S. SUMMERS. 

